From what I can work out from various sources (including the etsy page of Marie Wingate, who was there from 1986), the Haseley Manor Pottery was set up by Krystyna Young (who had restored the manor along with her husband Raymond) and closed following her death in around 1990. She had previously been at the Brading Pottery.

This pot is 10cm wide, inscribed on the base "Haseley Pottery" and "IW".